Robin van Persie celebrated in the manner of someone who wanted to respond to Arsène Wenger's assertion that he was still, deep down, an "Arsenal man". Yet again he had reminded his former club of his uncommon gifts and this time there was none of the restraint that had accompanied previous occasions. Van Persie was off, running to the touchline to embrace Wayne Rooney and to hell with the modern etiquette of suppressing these explosions of joy against old comrades.

What a valuable goal that could be for Manchester United and what a significant moment for David Moyes after all those settling-in issues as Sir Alex Ferguson's successor and the previous haul of one point from the three other fixtures, against Liverpool, Chelsea and Manchester City, that act as the benchmark for his new employer.

His team had to endure some concerted pressure and it was unashamed conservatism in the final exchanges when the electronic board went up to signal Marouane Fellaini was replacing Van Persie. Yet United gave everything to hold on to their lead.

At one point Rooney could be seen making a decisive tackle on the edge of his own penalty area. The next challenge was his as well, sprinting 70 yards to chase down a long, dropping ball, punted out of defence. The striker typified United's spirit of togetherness and Arsenal, despite plenty of the ball, just never had the wit to break them down even after Nemanja Vidic had gone off, spitting blood and wobbly enough to necessitate a hospital visit.

The whack to Vidic's head, in a collision with David de Gea, left him in an ambulance. Rio Ferdinand was already missing and, with Chris Smalling deputising for Rafael da Silva, United had to take on the league leaders for the last 45 minutes missing three-quarters of their first-choice defence.

In stoppage time Old Trafford held its breath as the Arsenal substitute Nicklas Bendtner tried to reach Bacary Sagna's right-wing delivery. Yet this was the wrong man at the right moment. Arsenal had played with a strange lack of creativity and it was mildly alarming Wenger talked so much about being inhibited by nervousness. Titles are never won with butterflies.

The mere fact Bendtner was on the pitch tells another story about the shortcomings that will encourage United to believe Arsenal's five-point lead can be whittled down. Moyes's team are now fifth, leapfrogging Everton, Tottenham and Manchester City to bring themselves within a point of Chelsea.

They have not lost for six weeks and their manager should discover that beating the team at the top of the league removes a lot of the crowd's uncertainty.

Arsenal will probably reflect Van Persie's headed goal might have been avoided if Per Mertesacker had been playing. As it was, their most imposing centre-half was missing because of a virus that had swept through their training ground over the last few days. Tomas Rosicky was also on his sickbed and, with other players possibly feeling the after-effects, maybe that contributed to why their usual sureness of touch was not always apparent.

Wenger, however, refused to make it an excuse and probably wisely bearing in mind Arsenal actually improved as the game went on. In the first half he felt his team had been held back by their own apprehension.

Yet these were experienced players. Mikel Arteta could be seen blindly kicking the ball straight to an opponent. Mesut Özil, of all people, tried a pass to the left and knocked it straight out of play. Olivier Giroud toiled away but with little success and, with Arsenal missing their usual refinement in midfield, the outstanding performer during the opening 45 minutes was United's Phil Jones, clattering into tackles, driving forward and fully justifying his selection ahead of Fellaini.

Jones was unfortunate to be booked for the accidental, yet jarring, clash of heads with Wojciech Szczesny and, after Vidic suffered his own Raging Bull moment, he went into central defence alongside Jonny Evans for the second half. United were guilty at times of defending too deeply. Arsenal flooded forward, with Jack Wilshere's introduction providing more thrust, but the new back four refused to buckle.

Smalling had one of his best games for some time, earning some rich words of praise from Moyes afterwards. The same player might have soothed Old Trafford's nerves with an unchallenged header at the other end from Patrice Evra's free-kick. The other outstanding chance of the second half fell Rooney's way, dragging a left-foot shot a yard wide.

Arsenal huffed and puffed but they created few noteworthy opportunities after that moment, 27 minutes in, when Rooney sent over a wonderfully taken corner and the visitors' preference for zonal marking meant Van Persie could attack the ball without anyone following his run.

That extra leverage, accelerating before the leap, was crucial to get above Giroud, who was trying to compensate because Aaron Ramsey had strayed from his position. Van Persie's header flashed past Szczesny and the victory run was very much that of a Manchester United man.